The present invention is directed to a process for forming images. More specifically, the present invention is directed to a process for forming images with a curable liquid, wherein the uncured liquid is applied to a substrate in imagewise fashion, a developer comprising fine particles is subsequently applied to the liquid image, and the liquid is then cured to fix the image. One embodiment of the present invention is directed to a process for forming images which comprises applying a curable liquid to a first substrate in an image pattern, optionally transferring the curable liquid image to a second substrate, subsequently contacting the curable liquid image with a solid developer so that the developer adheres to the curable liquid image, optionally transferring the curable liquid and the solid developer in image pattern to a third substrate, and curing the curable liquid in the image pattern to a solid.
Curable inks are known in the printing industry. For example, U.S. Pat. No. 4,680,368 (Nakamoto et al.), the disclosure of which is totally incorporated herein by reference, discloses an ultraviolet curable ink composition comprising a polyurethane polymethacrylate obtained by reacting a polyisocyanate compound of the formula ##STR1## wherein R.sub.1 is a hydrogen atom or a methyl group, and n is an integer of from 1 to 20, with a hydroxyl group containing methacrylate and having in one molecule at least two methacryloyl groups and at least two urethane bonds, a radical polymerizable low molecular weight compound, and a photopolymerization initiator.
In addition, U.S. Pat. No. 4,443,495 (Morgan et al.), the disclosure of which is totally incorporated herein by reference, discloses a heat curable conductive ink which comprises (1 ) an ethylenically unsaturated member of the group consisting of (a) a liquid ethylenically unsaturated monomer, oligomer, or prepolymer of the formula ##STR2## wherein R is H or CH.sub.3, R.sub.1 is an organic moiety and n is at least 2, (b) a polythiol in combination with (a), a polythiol in combination with a liquid ethylenically unsaturated monomer, oligomer, or prepolymer of the formula ##STR3## wherein R.sub.2 is H or CH.sub.3, R.sub.3 is an organic moiety and n is at least 2, and (d) mixtures of (a), (b), and (c); (2) a thermal initiator; and (3) an electrically conductive material. Heating of the composition in a desired pattern on a substrate results in a printed electric circuit.
Further, U.S. Pat. No. 4,751,102 (Adair et al.), the disclosure of which is totally incorporated herein by reference, discloses a radiation curable ink composition comprising pigment and a photohardenable composition, wherein the photohardenable composition comprises a free radical addition polymerizable or crosslinkable compound and an ionic dye reactive counter ion compound which is capable of absorbing actinic radiation and producing free radicals which initiate free radical polymerization or crosslinking of the polymerizable or crosslinkable compound.
Additionally, U.S. Pat. No. 4,334,970 (Lombardi et al.), the disclosure of which is totally incorporated herein by reference, discloses a photosensitive resin system that is essentially solvent free and contains an ester produced from an unsaturated organic acid and a polyhydroxyl containing material, a photoinitiator, a carbonyl initiator, a monomer capable of reacting with an acrylic monomer, and an unsaturated hydroxyl containing polymer hydrocarbon.
Further, "Photochemical Aspects of UV Curing," Y. C. Chang, Photographic Science and Engineering, Vol. 21, No. 6 (1977) discloses the electro-optical properties of UV-curing materials, the effect of pigment dispersion on the curing rate of inks containing pigments, and the spectroscopic calibration of the degree of UV cure.
U.S. Pat. No. 3,661,614, U.S. Pat. No. 4,003,868, and U.S. Pat. No. 4,215,167, the disclosures of which are totally incorporated herein by reference, also disclose ultraviolet curable printing inks.
U.S. Pat. No. 4,399,209 (Sanders et al.), the disclosure of which is totally incorporated herein by reference, discloses a transfer imaging system wherein images are formed by imagewise exposing a layer comprising a chromogenic material and pressure rupturable capsules containing, as an internal phase, a photosensitive composition. When a coated composition containing the chromogenic material and the encapsulated photosensitive composition is exposed to actinic radiation and the capsules are subsequently ruptured in the presence of a developer, the image-forming reaction between the chromogenic material and the developer discriminately occurs in the exposed or unexposed areas and produces a detectable image. This result is accomplished by controlling whether the chromogenic material can transfer from the imaging sheet to the developer sheet. Generally, the photosensitive composition has a viscosity that changes upon exposure to actinic radiation such that upon exposure there is a change in the viscosity of the internal phase in the exposed areas, which imagewise determines whether the chromogenic material is accessible to the developer. The photosensitive composition may be a radiation curable composition which, upon exposure to light, increases in viscosity and immobilizes the chromogenic material, thereby preventing it from transferring to the developer sheet and reacting with the developer material. Alternatively, the chromogenic material can be encapsulated with a substance which is depolymerized or otherwise decreased in molecular weight upon exposure, resulting in a decrease in viscosity which renders the chromogenic material accessible or transferrable to the developer in the exposed areas.
Liquid developers and liquid development processes for the development of electrostatic latent images are also known. In electrophoretic developers and processes, the liquid developers generally comprise a liquid vehicle and colored toner particles, and frequently also contain a charge control agent. The colored toner particles become charged, and upon contacting the electrostatic latent image with the liquid developer, the particles migrate through the liquid vehicle toward the charged image, thereby effecting development. Any residual liquid vehicle remaining on the image subsequent to development is evaporated or absorbed into the receiving sheet. Typically, liquid developers employ hydrocarbon liquid vehicles, most commonly high boiling aliphatic hydrocarbons that are relatively high in resistivity and nontoxic. Developers and processes of this type are disclosed in, for example, U.S. Pat. No. 4,476,210, U.S. Pat. No. 2,877,133, U.S. Pat. No. 2,890,174, U.S. Pat. No. 2,899,335, U.S. Pat. No. 2,892,709, U.S. Pat. No. 2,913,353, U.S. Pat. No. 3,729,419, U.S. Pat. No. 3,841,893, U.S. Pat. No. 3,968,044, U.S. Pat. No. 4,794,651, U.S. Pat. No. 4,762,764, U.S. Pat. No. 4,830,945, U.S. Pat. No. 4,686,936, U.S. Pat. No. 4,766,049, U.S. Pat. No. 4,707,429, U.S. Pat. No. 4,780,388, U.S. Pat. No. 3,976,808, U.S. Pat. No. 4,877,698, U.S. Pat. No. 4,880,720, U.S. Pat. No. 4,880,432, and copending application U.S. Ser. No. 07/300,395, the disclosures of each of which are totally incorporated herein by reference.
In polarizable liquid development processes, as disclosed in U.S. Pat. No. 3,084,043 (Gundlach), the disclosure of which is totally incorporated herein by reference, liquid developers having relatively low viscosity and low volatility and relatively high electrical conductivity (relatively low volume resistivity) are deposited on a gravure roller to fill the depressions in the roller surface. Excess developer is removed from the lands between the depressions, and as a receiving surface charged in image configuration passes near the gravure roller, liquid developer is attracted from the depressions onto the receiving surface in image configuration by the charged image. Developers and processes of this type are disclosed in, for example, U.S. Pat. No. 4,047,943, U.S. Pat. No. 4,059,444, U.S. Pat. No. 4,822,710, U.S. Pat. No. 4,804,601, U.S. Pat. No. 4,766,049, Canadian Patent 937,823, Canadian Patent 926,182, Canadian Patent 942,554, British Patent 1,321,286, and British Patent 1,312,844, the disclosures of each of which are totally incorporated herein by reference.
Liquid developers containing curable resins in a liquid vehicle such as an aliphatic hydrocarbon are also known, as disclosed, for example, in "Ultra-Violet Curable Liquid Immersion Development Toner," C. C. Chow, Xerox Disclosure Journal, Vol. 1, No. 5 (1976), Japanese Patent 62-115 171, Japanese Patent 62-018 575, Japanese Patent 62-018 574, Japanese Patent 61-156 264, Japanese Patent 61-156 263, Japanese Patent 61-156 262, Japanese Patent 61-156 261, Japanese Patent 61-060 714, Japanese Patent 63-155 055, and Japanese Patent 62-098 364. In addition, U.S. Pat. No. 4,764,447, Japanese Patent 62-007 718, Japanese Patent 62-007 717, Japanese Patent 62-007 716, Japanese Patent 62-004 714, Japanese Patent 61-020 056, and Japanese Patent 60-249 156 disclose processes for polymerizing monomers in a hydrocarbon liquid vehicle to form dispersions of polymer particles suitable for use as liquid developers. Further, Japanese Patent 62-014168 discloses an encapsulated toner contained in a liquid vehicle. The capsule core can be cured by heat, and the monomers or oligomers become fixed to paper when images developed with the developer are cured.
U.S. Pat. No. 4,881,084 (Kan et al.), the disclosure of which is totally incorporated herein by reference, discloses a process of recording using fluid ink which is substantially non-adhesive but can be imparted with an adhesiveness upon application of an energy such as electrochemical energy or heat energy. The ink is obtained by impregnating a crosslinked substance such as guar gum or polyvinyl alcohol with a liquid dispersion medium such as water. The fluid ink, preferably formed into a layer in advance, is supplied with a pattern of energy to be provided with an adhesive pattern, which is then transferred to a recording medium, such as plain paper, directly or by the medium of an intermediate transfer medium to form an ink pattern corresponding to the energy pattern applied. If desired, the ink pattern can be developed with toner particles at a point downstream from the ink contact position.
U.S. Pat. No. 4,943,816 (Sporer), the disclosure of which is totally incorporated herein by reference, discloses a printer suitable for color printing which uses an ink printhead in which the marking fluid contains no dye so that a latent image of the desired print pattern is produced in the form of moistened spots directly on the print medium. The latent image is then developed by applying colored powder to the print medium, and the developed image is then fixed to the print medium to produce a visible image of the desired print pattern.
U.S. Pat. No. 4,303,924 (Young), the disclosure of which is totally incorporated herein by reference, discloses a jet drop printing process utilizing a radiation curable ink composition. The ink composition includes a low molecular weight multifunctional ethylenically unsaturated material, a low molecular weight monofunctional ethylenically unsaturated material, a reactive synergist, a dye colorant, and an oil soluble salt. A small amount of organic polar solvent and stabilizer may also be included. In addition, when a UV cure is used, a photoinitiator is also added to the mixture. The ink has a viscosity of less than about 15 centipoise, a resistivity of from 50 to 5,000 ohm-cm, and a surface tension of about 20 to 70 dynes per centimeter.
U.S. Pat. No. 4,604,340 (Grossa), the disclosure of which is totally incorporated herein by reference, discloses a process for the production of patterns on a substrate bearing a layer of a negative-working, light-sensitive composition comprising at least one 1,4-dihydropropyridine compound substituted in the 4 position by a 2'-nitrophenyl ring which becomes tacky and tonable on exposure to actinic radiation. The process comprises the steps of exposing the light sensitive layer imagewise to actinic radiation whereby tacky areas are formed, and toning the exposed tacky areas with finely divided powders.
U.S. Pat. No. 4,832,984 (Hasegawa et al.), the disclosure of which is totally incorporated herein by reference, discloses a method for forming an image comprising a step of applying ink to a recording medium having a light transmissive ink retaining layer and a light diffusing ink transporting layer on a substrate to form an image through the ink transporting layer in the ink retaining layer and a step of transparentizing the ink transporting layer.
U.S. Pat. No. 3,275,436 (Mayer), the disclosure of which is totally incorporated herein by reference, discloses a process of forming image reproductions which comprises in sequence the steps of presenting an adhesively tacky support base surface bearing a resist image into contact against a second support base containing a releasable uniform surface film selectively by area subjected to adhesive attraction, and separating the support bases from each other whereby the film from the second support base is released to the first support base in the surface areas devoid of the resist image.
Copending application U.S. Ser. No. 07/654,693, entitled "Curable Liquid Developers," with the named inventors Ian D. Morrison, Bing R. Hsieh, and Jerry H. Taylor, the disclosure of which is totally incorporated herein by reference, discloses a liquid developer comprising a colorant and a substantial amount of a curable liquid vehicle having a viscosity of no more than about 500 centipoise and a resistivity of no less than about 10.sup.8 ohm-cm.
While known processes are suitable for their intended purposes, a need remains for processes for forming images that overcome the disadvantages of known imaging methods. For example, while liquid electrophotographic development processes enable the generation of high quality and high resolution copies, one difficulty frequently encountered is an objectionable odor that typically accompanies liquid development processes. The sources of this odor are solvent vapors emitted from the copier or printer and the slow release of vapor from residual liquid vehicle remaining on the receiver sheet. A file drawer containing several documents prepared by liquid development processes can accumulate vapor to an unacceptable level. Accordingly, the reduction of solvent vapor emissions from liquid developing machines and from prints prepared with liquid developers is highly desirable for environmental and aesthetic purposes. In addition, ink jet printing processes using inks comprising soluble dyes can exhibit many problems, such as poor waterfastness, poor lightfastness, clogging of the jetting channels as a result of solvent evaporation and changes in the dye's solubility, dye crystallization, ink bleeding when prints are formed on plain papers, poor thermal stability, chemical instability, ease of oxidation, and low drop velocity. In addition, many of the dyes contained in inks may be potentially mutagenic. These problems can be minimized by replacing some of the dyes used in ink formulations with insoluble pigments. In general, pigments have superior properties with respect to dyes, such as good waterfastness, good lightfastness, good image density, thermal stability, oxidative stability, the ability to perform intercolor ink mixing, compatibility with both coated/treated and plain papers, and non-mutagenic properties. Pigment based inks, however, also exhibit difficulties, such as the pigment particles not remaining dispersed and precipitating from the liquid vehicle. Further, both dye based and pigment based inks exhibit the problem of nozzle clogging in ink jet printers, particularly when the printer has not been used for a period of time.
Thus, a need continues to exist for printing processes that produce prints with little or substantially no odor. A need also remains for printing processes that reduce or substantially eliminate the emission or carryout of solvent vapors from copiers and printers employing liquid inks. Further, there is a need for printing processes that enable the generation of high quality images. Additionally, a need exists for printing processes that reduce or eliminate the need to dispose of solvents from a copier or printer employing liquid inks. Further, there is a need for printing processes that enable formation of images with excellent fix to a substrate. In addition, a need remains for printing processes that enable simplified containment and capture procedures for reducing or eliminating solvent emissions for copiers or printers employing liquid inks. There is also a need for printing processes that overcome many of the difficulties commonly encountered in ink jet printing processes, such as poor waterfastness, poor lightfastness, clogging of the jetting channels, dye crystallization, ink bleeding when prints are formed on plain papers, poor thermal stability, chemical instability, ease of oxidation, and low drop velocity. A need also exists for printing processes with colored particulate materials which are not suitable for use in conventional electrostatic development processes such as xerography. Further, there is a need for printing processes that enable the use of materials that might not be stable in a liquid ink composition or in an electrographic powder toner, such as fibers, thin walled capsules, metallic particles, or the like, but can be applied to a curable liquid image by, for example, forming a donor layer of the material and applying it to the liquid image, followed by curing of the liquid. Additionally, there is a need for printing processes that enable creation of a high contrast, positive-negative pair of images.